Quantum Coherence and the Kondo Effect in the 2D Electron Gas of Magnetically Undoped AlGaN/GaN High-Electron-Mobility T
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INTERNATIONAL SYMPOSIUM “NANOPHYSICS AND NANOELECTRONICS”, NIZHNY NOVGOROD, MARCH 10–13, 2020
Quantum Coherence and the Kondo Effect in the 2D Electron Gas of Magnetically Undoped AlGaN/GaN High-Electron-Mobility Transistor Heterostructures N. K. Chumakova,*, I. A. Chernykha, A. B. Davydovb, I. S. Ezubchenkoa, Yu. V. Grishchenkoa, L. L. Levc,d, I. O. Maiborodaa, L. A. Morgunb, V. N. Strocovd, V. G. Valeyeva, and M. L. Zanaveskina a National
Research Center “Kurchatov Institute”, Moscow, 123182 Russia Lebedev Physical Institute, Russian Academy of Sciences, Moscow, 119991 Russia c Moscow Institute of Physics and Technology, Dolgoprudnyi, Moscow oblast, 141701 Russia d Swiss Light Source, Paul Scherrer Institute, CH-5232, Villigen-PSI, Switzerland *e-mail: [email protected] b
Received April 15, 2020; revised April 21, 2020; accepted April 21, 2020
Abstract—The unusual observation of the Kondo effect in the two-dimensional electron gas (2DEG) of magnetically undoped AlGaN/GaN heterostructures is reported. The temperature-dependent zero-field resistivity data exhibits an upturn below 120 K, while the standard low-temperature weak localization and then weak antilocalization behaviour is revealed at T → 0. Magnetic transport investigations of the system are performed in the temperature range of 0.1–300 K and at magnetic fields up to 8 T, applied perpendicularly to the 2DEG plane. The experimental data are analyzed in terms of the multichannel Kondo model for d0 magnetic materials and weak localization theory taking into account the spin-orbit interaction. Keywords: nitride heterostructures, two-dimensional electron gas (2DEG), d0 magnetism, Kondo effect, spin-orbit interaction DOI: 10.1134/S1063782620090067
1. INTRODUCTION AlGaN/GaN wurtzite heterostructures and highelectron-mobility transistors (HEMTs) based on them have been actively investigated in recent decades as potential candidates for fabrication of the next generation of high-power, high-temperature, and microwave electronics. This interest is due to the fact that current densities, working temperatures, breakdown voltages, and cutoff frequencies, obtained there, are considerably higher when compared with the similar properties of all occurring systems based on GaAs, Si, and Ge [1]. These properties are unique and conditioned by the presence of a two-dimensional electron gas (2DEG) in there with a carrier concentration of ~1013 cm–2 localized in the vicinity of the interface of the heterostructure materials without special doping. This value is an order of magnitude larger than the electron density attainable in other structures based on III–V materials [2]. Appearance of the high-density 2DEG is attributed to the formation of a deep spikeshaped quantum well at the heterojunction, where a large conduction band offset coexists with large piezoelectric and spontaneous polarization [3].
Despite considerable progress in the development of III-nitride functional systems, this family of semiconductor materials continues to bring surprises. In this work, we re
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